OBJECTIVE: Clinicians may benefit from using a joint mobility index to screen for individuals on the high end of the spectrum of joint laxity (ie, those with generalized joint laxity), which may be associated with musculoskeletal complaints. Reliability of the Beighton and Horan Joint Mobility Index (BHJMI) has not been reported in the literature. Our purpose was to determine intrarater and interrater reliability of (1) composite BHJMI scores (the overall score from 0 to 9), and (2) categorized scores, the BHJMI scores in 3 categories (0 to 2, 3 to 4, and 5 to 9) DESIGN AND SETTING: This was an intrarater and interrater reliability study. Data were collected in an academic physical therapy department and in a high school. SUBJECTS: Forty-two (intrarater) and 36 (interrater) female volunteers, aged 15 to 45 years. MEASUREMENTS: Subjects were screened using the BHJMI. Percentage agreement and the Spearman rho were used to analyze BHJMI composite and category scores. RESULTS: The percentage agreement and the Spearman rho for intrarater and interrater reliability of BHJMI composite scores were 69% and.86 and 51% and.87, respectively. The percentage agreement and the Spearman rho for intrarater and interrater reliability of the category scores were 81% and.81 and 89% and.75, respectively. CONCLUSIONS: Reliability of the BHJMI was good to excellent in screening for generalized joint laxity in females aged 15 to 45 years.